A so-called SWS (Still With Sound) method has been proposed which comprises the steps necessary to record, on a recording disk, control information in addition to audio information digitized together with video information, and to regenerate at the time of the regenerative operation the audio information according to the control information. Thus, sound may be added to corresponding still image information. In this method, an adaptor has been developed in order that an ordinary VDP (video disk player) can be additionally provided with an SWS processor which regenerates and processes the audio information and the control data (hereinafter referred to as SWS data).
Since the SWS processor may properly read the SWS data if the VDP is in the normal regenerative mode, forward-framing regenerative mode, still image regenerative mode, or the like, it is sufficient for the SWS processor to carry out signal processing according to the content of properly read data. However, the SWS processor is not able to read the SWS data properly when the VDP is in certain specific regenerative modes such as reverse regenerative mode, fast-forward regenerative mode, or the like. Therefore, data must not be sent to the control circuit during any of the latter specific regenerative modes. Accordingly, a circuit configuration is required which enables the SWS processor to automatically discriminate the current VDP operation mode.